Amplitude-dependent damping and acoustoplastic effect in crystals

The acoustoplastic effect (APE) and the damping of superimposed vibrations responsible for this effect are investigated. The results show the following. The damping consists of two parts: dynamic and structural. The former decreases and the latter increases with increasing amplitude of vibrations. The amplitude-dependent dynamic internal friction and the acoustoplastic effect can be phenomenologically described by a superposition of static and vibrational loads. The structural internal friction shows the absence of an additional damping associated with the APE. It is concluded that the superposition approach is not enough to explain all peculiarities of the APE. The amplitude-dependent damping indicates that the APE cannot be attributed to the heating of the sample under the vibrations. There is evidence for the reversible changes of dislocation structure. Hence, internal stresses also may be affected by superimposed vibrations. These mechanisms are discussed within the framework of available theories and experimental data.